The employment of a conformal polydopamine thin layer reduces the cytotoxicity of silver nanoparticles

Abstract

Silver nanoparticles (AgNPs) with their unique properties represent great promise in biological applications. However, thehigh toxicity of AgNPs still remains a major bottleneck and hinders their basic usage. In the present study, to improve the cytotoxicityof AgNPs, a thin layer of polydopamine (PDOP) was proposed as shell material. For this, the as-prepared citrate-stabilized AgNPs weredispersed in dopamine solution under alkaline conditions. The thickness of the PDOP layer could be manipulated simply by tuningthe polymerization time. It was indicated that all NP systems (PDOP, AgNP, and AgNP@PDOP) were efficiently synthesized in thedesired size and morphology. Cytotoxicity tests of all NP systems were performed in the Caco2 cell line and the results were evaluatedthrough sulforhodamine B (SRB) assay. Due to their natural characteristics, even at low concentrations (12.5 ppm) AgNPs exhibitedhigh cytotoxicity. In contrast, PDOP had almost no toxic effect on cells at high concentrations (200 ppm). The employment of a thinlayer of PDOP (5 ± 1 nm) distinctively improved the cytotoxicity of the AgNP@PDOP NP system without any change of optoelectronicproperties of AgNPs. A dose of 200 ppm of AgNP@PDOP NPs did not create any toxicity and the cells preserved their interaction,morphology, and cellular integrity.